ABSTRACT Our long-term goal is to understand visuospatial processing in the brain and the neural mechanisms underlying visually-guided movements. Most actions involve coordination across multiple body parts, and so understanding coordination is instrumental to understanding visuomotor processing in general. We will look specifically at the coordination of the two hands (bimanual coordination) and the eye and hand (eye-hand coordination) in the macaque monkey. In this grant cycle, we focus on the parietal reach region (PRR) in the posterior parietal cortex, a key nexus of sensory, motor and attentional processing. In future cycles, we will extend these studies to other brain areas. Our first aim elucidates the role PRR plays (if any) in bimanual coordination. We focus on ipsilateral limb information in PRR and on interhemispheric communication. We will record from neurons during different types of bimanual coordination tasks, all of which require synchronous behavior of the two hands. We will quantify the synchrony of behavior and then determine whether and how PRR activity (single units and LFP) reflects the type of bimanual coordination task and the level of synchrony that is actually achieved. We will also assess information transfer across the two hemispheres and ask if this varies by task and degree of coordination. Our second aim is similar, but adds in the additional dimension of eye movements, spontaneously deployed by animals as they perform these tasks. We will evaluate whether and how PRR reflects different patterns of eye-hand coordination. Our final aim addresses the coding of static eye and hand positions in a bimanual task. In the previous grant cycle, we described an encoding of the distance between gaze and hand in PRR during a unimanual task. Based upon the format of that encoding, we argued that PRR plays a role in reference frame transformations. Discovering whether and how this encoding is maintained in a bimanual task - when there are two eye-hand distances rather than only one to encode - will provide critical information about what computations can or cannot be performed in PRR, and will provide further evidence for, or against, the hypothesis that PRR is involved in bimanual and/or eye-hand coordination. The paradigms we are developing should allow us to identify signals in PRR and elsewhere that are related to motor coordination. Achieving our aim will advance our understanding of the role of PRR in bimanual and eye-hand coordination and also provide invaluable information about how cross-effector and cross-system coordination is achieved in the brain.